You shard by user ID. 80% of writes go to 20% of shards because your top customers are assigned to the same shards. Or you shard by date and all writes go to the current month's shard. Uneven distribution turns a scaling solution into a bottleneck.
Understand JWT stateless tradeoffs, session cookie security, token refresh rotation, and hybrid approaches. Learn when to use JWTs for service-to-service auth and why short TTLs matter.
Build real-time AI systems with Kafka as your event backbone. Ingest features, trigger training, distribute model outputs, and sync data to vector DBs at scale.